二衬厚度对盾构隧道双层衬砌纵向力学性能的影响

盾构隧道作为一种复杂的三维线性地下结构,容易受围岩特性不均等因素影响产生不均匀变形,引发结构局部破坏等病害。为研究双层衬砌盾构隧道在运营过程中的纵向力学行为,结合武汉地铁8号线越江隧道工程,建立纵向三维壳-弹簧力学分析模型,结合工程实际探讨二次衬砌厚度对盾构隧道双层衬砌力学性能的影响,以期获取合理的二次衬砌厚度取值。研究结果表明:(1)盾构隧道双层衬砌结构的纵向等效弯曲刚度随二次衬砌厚度增加呈线性增加;(2)施作二次衬砌可降低隧道纵向不均匀沉降量及管片间的错台量,二者随二次衬砌厚度增加而减小,但幅度不大;(3)在隧道纵向出现极端不均匀变形条件下,施作二次衬砌会导致位移突变点附近部位的管片局部内力及环缝张开量增大;(4)综合分析盾构隧道管片衬砌变形及受力,同时考虑工程造价和二衬是否设置配筋等因素,对于直径12 m级盾构隧道,其二次衬砌厚度建议取20~35 cm。

The Influence of the Thickness of Secondary Lining on the Longitudinal Mechanical Properties of Shield Tunnel With Double-layer Lining

Shield tunnel is a complex three-dimensional long-line underground structure and it is vulnerable to uneven deformation caused by uneven characteristics of surrounding rocks and other factors. Such deformation may lead to damages such as local failure of the shield tunnel. In order to study the longitudinal mechanical behavior of the double-layer lining shield tunnel during operation, a longitudinal three-dimensional shell-spring mechanical analysis model is established with reference to Wuhan Metro Line 8 cross-river tunnel project. This paper discusses the influence of the secondary lining thickness on longitudinal mechanical properties of the shield tunnel with double-layer lining, and proposes the reasonable thickness of the secondary lining. The results show that 1) the longitudinal equivalent bending stiffness of the double-layer lining structure of the shield tunnel increases linearly with the increase of the thickness of the secondary lining; 2) the application of the secondary lining reduces the longitudinal non-uniform settlement of the tunnel and the segment dislocation, both of which decrease with the increase of the thickness of the secondary lining, but the amplitude is not large; 3) under the condition of extremely uneven deformation in the longitudinal direction of the tunnel, the local internal force of segment and the longitudinal crack of shield tunnel segment joint near the catastrophe point of displacement will increase if the secondary lining is constructed; 4) the thickness of the secondary lining of shield tunnels with diameter of 12 m is suggested to be 20-35 cm based on comprehensive analysis of the deformation and stress of the segment lining of shield tunnels, and the consideration of the construction cost and reinforcement of the second lining.